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Some Aspects of Population Dynamics of Tenualosa Ilisha (hamilto) from the Khulna Offshore Region

S. M. Nurul Amin
Bangladesh Fisheries Research Institute, Riverine Station, Chandpur, Bangladesh.

M. A. Rahman
Bangladesh Fisheries Research Institute, Riverine Station, Chandpur, Bangladesh.

G. C. Haldar
Bangladesh Fisheries Research Institute, Riverine Station, Chandpur, Bangladesh.

M. A. Mazid
Bangladesh Fisheries Research Institute, Riverine Station, Chandpur, Bangladesh.

Abstract/ Executive Summary:

Population parameters of Tenualosa ilisha were estimated using FiSAT softwere with length-frequency data collected from the khulna offshore region of Bangladesh. The von Bertalanffy growth parameters L_oo and K for species were 52.78 cm and 0.91/ year respectively. The annual rate of natural (M) and fishing mortality (F) were found to be 1.43 and 1.74 respectively. The estimated values of the exploitation rate (E) using length converted catch curve and Virtual Population Analysis were 0. 548 and 0.402 respectively. The recruitment of this species was continuous with two peaks per year i. e. one in February and another in August,. E_maxwas found to be 0.675. The study shows some over fishing of T. ilisha (E> 0.50) in the Khulna offshore waters. The estimated length-weight relationship for the combined sex was found to be W= 0.011TL^3.038

Keywords: Fish, Stock assessment, Khulna area

Location: different landing centres of Khulna region.

Start Date: 00-01-1997

End Date: 00-12-1997

Program Area: Resource Development and Management

Commodity: Hilsa

Objectives:

To the population dynamics and stock assessment of this species in the Khulna offshore region.

Methodology:

Length-frequency data of T. ilisha were collected fortnightly from different landing centres of Khulna region from January to December 1997. The total length and weight of 1251 specimens were measured in cm by a metre scale (1 ± mm) and weight in g by a Salter spring balance respectively. The data were pooled month wise form different landing sites and subsequently grouped into classes of one-cm intervals. The data were analysed using the FiSAR (FAO-ICLARM Stock Assessment Tools) as explained by Gayanilo et al. (1996). Asymptotic length (L_oo) and growth co-efficient (K) of the von Bertalanffy equation for growth in length were estimated by means of ELEFAN-I.Relative yield-per-recruit (Y/R) and relative biomass-per-recruit (R/B) values as a function of E were determined from the estimated growth parameters and probability of capture by length . The calculations were carried out using the complete FiSAT softwere package. An estimated length structure VPA of T. ilisha was carried out Loo= 52.78, K=0.91/yr, M= 1.43, F=1.74, a = 0.011 and b= 3.038 were used as imput to a VPA.

Source of Information: The Journal of Noami Vol-17, No. 1 & 2, Dec: 2000

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the results of this investigation, it can be concluded that the T. ilisha is a moderate sized fish having perfect growth rate. Recruitment patterns of the fish reveal that it recruits in the fishery almost all of the year. Its fishing mortality is high and need to be reduced for getting more sustained production. Some fishing restriction should be imposed to get higher fish yield from that region.

Knowledge Management: Journal